Magenta inkjet ink having improved print quality with porous photo media

ABSTRACT

The present invention relates to magenta dye-based inkjet inks having improved permanence when jetted onto porous photo media. The inkjet ink includes a mixture of at least two magenta dyes, at least three co-solvents comprising about 18 to about 24% of the composition of the ink by weight, a penetrant, at least one wetting agent, and water.

CROSS REFERENCE TO RELATED APPLICATIONS

Not applicable.

MICROFICHE APPENDIX

Not applicable.

GOVERNMENT RIGHTS IN PATENT

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to inkjet inks, and, more particularly, tomagenta inkjet inks having improved print quality with porous media.

2. Description of the Related Art

Thermal inkjet printing, to which this invention relates, is a commonlypracticed form of printing. Thermal inkjet printing involves intenseheating of an aqueous ink in a small amount in contact with a heatingelement so the ink is vaporized. The vaporized ink, including solids inthe ink, is then expelled through a nozzle and subsequently jetted to anintended substrate, such as, for example, paper.

The composition of an inkjet ink is traditionally comprised of deionizedwater, a water-soluble organic solvent, and a colorant. The colorant maybe a soluble dye or insoluble pigment. Traditionally, pigment based inksmay have some disadvantages as compared to dye based inks as traditionalpigment based inks tend to have slightly higher solids and viscositywhich may pose to be more difficult for jetting through relativelysmaller nozzle printhead designs. For example, due to the insolubilityof pigments in water, polymeric dispersants and/or surfactants aretypically added to improve the dispersibility of the pigment. Theaddition of a polymeric dispersant can increase the viscosity of an ink,and a viscous ink may be more difficult to jet in a printhead.

Inkjet printers may use dye-based color inks or pigment-based colorinks. Dye-based color inks tend to be more saturated and more robust toinkjet pens. In contrast, pigment-based color inks tend to be morepermanent and of the quality typically recognized with laser-likeprinters.

There is a very limited choice of pigments for use with pigment-basedcolor inks, whereas the number of dyes to be used with dye-based colorinks continuously grows.

A current challenge in the industry is to develop faster dryingdye-based inks for use with porous photo media, rather than for use withtraditional swellable polymer photo media. However, porous photo mediaare comprised of inorganic materials that, in conjunction with ozonegasses and light, interact with dyes such that the dyes fade anddegrade.

What is needed in the art is a magenta dye-based inkjet ink that may beused with porous photo media with substantially minimal fading anddegradation of the magenta dye.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide an inkjet inkcomprised of a mixture of two or more magenta dyes, at least threeco-solvents comprising about 18% to about 24% of the composition of theink by weight, a penetrant, at least one wetting agent, and water.

Various other exemplary embodiments of the present invention include amethod of printing using an inkjet ink. The method is comprised of thesteps of positioning a porous photo medium substantially adjacent to aprinter having a print head retaining an inkjet ink, wherein the inkjetink is comprised of a mixture of two or more magenta dyes, at leastthree co-solvents comprising about 18% to about 24% of the compositionof the ink by weight, a penetrant, at least one wetting agent, andwater. The inkjet ink is then jetting from the print head onto theporous photo medium.

DETAILED DESCRIPTION OF THE INVENTION

Porous photo media, as opposed to traditional swellable polymer photomedia, tends to allow for faster drying. As such, it is desired todevelop dye-based inks that allow greater permanence with the porousphoto media. However, as noted above, porous photo media are comprisedof inorganic materials that, in conjunction with ozone gasses and light,interact with dyes such that the dyes fade and degrade.

Permanence, as used herein, refers in part to the ability of a dye toresist the interactions with light, ozone, temperature, and humiditythat cause fading and degradation of the dye associated with the media.

It has been found that a color inkjet ink having a mixture of two ormore magenta dyes, three co-solvents, a penetrant, and a wetting agenthas an increased permanence when used with porous photo media.

In exemplary embodiments, the inkjet ink may further be comprised of abiocide, such as, for example, PROXEL® GXL (available from ArchChemicals, Inc. of Norwalk, Conn.).

In the various exemplary embodiments of the present invention, themixture of two or more magenta dyes of the inkjet ink comprises about3.0% to about 6.0% of the composition of the ink by weight. In apreferred embodiment, the mixture of two more magenta dyes comprisesabout 4.0% of the composition of the ink by weight.

The mixture of two more magenta dyes may include dyes selected from thegroup consisting of Nippon Magenta JPD LM-1 Liquid (an anthrapyridonedisulfonic acid available from Nippon Kayaku Co, Ltd of Tokyo, Japan)and a magenta dye as described in U.S. Pat. No. 5,254,160 (availablefrom Lexmark International, Inc. of Lexington, Ky.), the chemicalstructure of which is:

wherein M is H, Li, Na, or K. Although the color is visually moreappealing with the magenta dye as described in U.S. Pat. No. 5,254,160,the Nippon Magenta JPD LM-1 Liquid is more lightfast on porous media.

In an exemplary embodiment, the amount of each of Nippon Magenta JPDLM-1 Liquid and a magenta dye as described in U.S. Pat. No. 5,254,160are substantially equal. In another exemplary embodiment, the amount ofeach dye in the mixture is about 2%.

In particular, the color of the Nippon Magenta JPD LM-1 Liquid may betoned by being further combined with one or more of dyes selected fromAcid Red 35, Acid Red 52, Acid Red 81, Acid Red 92, Acid Red 249, AcidRed 289, Direct Red 289, Direct Red 227, Direct Violet 107 (availablecommercially as PROJET® Magenta 2 from Fujifilm of Tokyo, Japan),PROJET® Magenta 3BOA (available commercially from Fujifilm of Tokyo,Japan), DUASYN® Magenta NM-SF (available commercially from Clariant ofCoventry, R.I.), ILFORD® M377 (available commercially from Ilford ofMarly, Switzerland), and combinations thereof.

The at least three co-solvents are selected from the group consisting of1,3-propanediol; 1,2-alkanediol; 1,5-pentanediol; triethylene glycol;and dipropylene glycol.

In exemplary embodiments, at least two of the three co-solvents arealkanediols and the third co-solvent is a glycol.

The penetrant is preferably about 1.0% to about 3.5% of the compositionof the ink by weight. A exemplary penetrant is 1,2-hexanediol.

It is preferred that the wetting agent be of about 0.5% to about 1.5% byweight of the inkjet ink. In a more preferred embodiment, the non-ionicsilicone surfactant is about 0.75% by weight of the inkjet ink.

Exemplary wetting agents include polyoxyethylene dimethyl siloxanes,ZONYL® fluorosurfactants, and combinations thereof. A commerciallyavailable wetting agent is, for example, SILWET® L-7600 (polyalkyleneoxide grafted polydimethylsiloxane from Momentive Performance).

The polymeric dispersant is preferably about 0.5% to about 2.0% byweight of the inkjet ink, and assists in stabilizing the carbon blackpigment and buffering the pH of the inkjet ink.

An optional polymeric dispersant can be added to assist in stabilizingthe compatibility with a carbon black pigment ink in aCyan-Magenta-Yellow-Black (CMYK) inkset. When CMYK inks are printed insubstantially close proximity to each other, each ink needs to becompatible and not destabilize adjacent inks. In the present exemplaryembodiments, the CMY dye inks may be printed along with a blackpigmented ink without destabilizing any of the CMY dye inks or the blackpigmented ink due to the presence of the polymeric dispersant in the Cdye inks.

In exemplary embodiments of the present invention, the polymericdispersant may be selected from dispersants set forth in, for example,any of U.S. Pat. Nos. 5,719,204; 5,994,427; 6,063,834; 6,267,807;6,896,724; and 6,984,701, all incorporated by reference.

One or more buffers may also be included in the inkjet ink composition.Exemplary embodiments of the one or more buffers include triethanolamine(TEA), N,N-bis(2-hydroxyethyl)tuarine orN,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid (BES), orcombinations thereof.

Several exemplary inkjet inks according to the present invention wereformulated and evaluated using a standard printhead and porous photopaper in the form of Perfectfinish Glossy Photo Paper (available fromLexmark International, Inc. of Lexington, Ky.). The same printing wasconducted using a commercially available magenta dye-based inkjet ink.Each ink was evaluated for its permanence against the effects of ozoneand xenon light.

In Table 1, the permanence of each dye-based ink on porous photo mediais compared. The numbers shown represents the number of years ofpermanence according to the criteria of 40% density loss and assumingthe exposure level of 78 ppm-hr/yr for ozone and 1.1 Mlux-hr/yr forlight fade.

TABLE 1 Permanence of Dye with Porous Photo Media Years of Permanenceafter Exposure to: Ozone Ink (1 ppm or 5 ppm) Xenon LF (80 klux) MagentaInkjet Ink 4 8 Commercially Available 1 7 Magenta-dye Based Inkjet Ink

As clearly illustrated above, the present magenta-dye based inkjet inkshows an improvement in permanence when exposed to ozone four timesgreater than that of commercially available magenta-dye inkjet inksundergoing the same exposure. When exposed to xenon light, the magentainkjet ink of the present invention showed a permanence 114% greaterthan that of a commercially available magenta-dye inkjet ink.

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which, this invention pertains andwhich fall within the limits of the appended claims.

1. An inkjet ink comprising: a mixture of at least two magenta dyes; at least three co-solvents comprising about 18% to about 24% of the composition of the ink by weight; a penetrant; a wetting agent selected from the group consisting of polyoxyethylene dimethyl siloxanes, fluorosurfactants, and combinations thereof; a polymeric dispersant about 0.5% to about 2.0% by weight of the inkjet ink; and water.
 2. The inkjet ink according to claim 1, wherein the at least two magenta dyes comprise about 3.0% to about 6.0% of the composition of the ink by weight.
 3. The inkjet ink according to claim 1, the mixture of at least two magenta dyes includes an anthrapyridone disulfonic acid liquid magenta dye and a magenta dye having the chemical structure:

wherein M is H, Li, Na, or K.
 4. The inkjet ink according to claim 3, wherein the amount of each of the anthrapyridone disulfonic acid liquid magenta dye and the magenta dye having the identified chemical structure is substantially equal.
 5. The inkjet ink according to claim 3, wherein the anthrapyridone disulfonic acid liquid magenta dye is toned with one or more of Acid Red 35, Acid Red 52, Acid Red 81, Acid Red 92, Acid Red 249, Acid Red 289, Direct Red 289, Direct Red 227, or Direct Violet
 107. 6. The inkjet ink according to claim 1, wherein the at least three co-solvents are selected from the group consisting of 1,3-propanediol; 1,2-alkanediol; 1,5-pentanediol; triethylene glycol; and dipropylene glycol.
 7. The inkjet ink according to claim 1, wherein two of the at least three co-solvents are alkanediols and the third co-solvent is a glycol.
 8. The inkjet ink according to claim 1, wherein the wetting agent is about 0.5% to about 1.5% of the composition of the ink by weight.
 9. The inkjet ink according to claim 1, further comprising one or more buffers selected from the group consisting of triethanolamine (TEA), N,N-bis(2-hydroxyethyl)tuarine, N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid (BES), and combinations thereof.
 10. The inkjet ink according to claim 1, further comprising a biocide.
 11. The inkjet ink according to claim 1, wherein the penetrant is a 1,2-alkanediol.
 12. A method of printing utilizing an inkjet ink, the method being comprised of the steps of: positioning a print medium substantially adjacent to a printer having a print head retaining an inkjet ink, wherein the inkjet ink is comprised of a mixture of at least two magenta dyes; at least three co-solvents comprising about 18% to about 24% of the composition of the ink by weight; a penetrant; a wetting agent selected from the group consisting of polyoxyethylene dimethyl siloxanes, fluorosurfactants and combinations thereof; a polymeric dispersant about 0.5% to about 2.0% by weight of the inkjet ink; and water; jetting the inkjet from the print head onto a porous photo medium.
 13. The method of printing utilizing an inkjet ink according to claim 12, wherein the mixture of at least two magenta dyes comprises about 3.0% to about 6.0% of the composition of the ink by weight.
 14. The method of printing utilizing an inkjet ink according to claim 12, the mixture of at least two magenta dyes includes an anthrapyridone disulfonic acid liquid magenta dye and a magenta dye having the chemical structure

wherein M is H, Li, Na, or K.
 15. The method of printing utilizing an inkjet ink according to claim 14, wherein the amount of each of the anthrapyridone disulfonic acid liquid magenta dye and the magenta dye having the identified chemical structure is substantially equal.
 16. The method of printing utilizing an inkjet ink according to claim 12, wherein the at least three co-solvents are selected from the group consisting of 1,3-propanediol; 1,2-alkanediol; 1,5-pentanediol; triethylene glycol; and dipropylene glycol.
 17. The method of printing utilizing an inkjet ink according to claim 12, wherein the wetting agent is about 0.5% to about 1.5% of the composition of the ink by weight.
 18. The method of printing utilizing an inkjet ink according to claim 12, further comprising one or more buffers selected from the group consisting of triethanolamine (TEA), N,N-bis(2-hydroxyethyl)tuarine, N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid (BES), and combinations thereof. 